This invention relates generally to inertial measurement systems and more specifically to measuring changes in angular acceleration around an axis.
In certain systems, it is desirable to measure changes in angular acceleration. Such systems include inertial navigation systems. In many inertial navigation systems, gyros are mounted in gimbals, allowing the gyro to move freely relative to the gimbals. The gimbals are affixed to some object being navigated. As is known, the axis of the gyro tends not to rotate in relation to an inertial coordinate system. If the object rotates, the gimbals move to compensate for the fact that the gyro does not rotate. The position of the gimbals thus gives an indication of the angular motion of the object being navigated. Appropriate steering commands can then be generated.
A problem arises because the gyro has associated with it a natural frequency of nutation. Even small amounts of force applied to the gyro at this natural frequency can cause the gyro to precess or nutate around its axis of rotation. The position of the gimbals then would no longer indicate the position of the object.
In some inertial navigation systems, active damping is used to avoid problems of nutation of the gyros. A rate of angular acceleration sensor is mounted on the gimbals. When this sensor produces a signal indicating the gyro is nutating, an electronic circuit actuates a control circuit which applies forces to the gyro. These forces counteract the nutation.
Existing rate of angular acceleration sensors are precision devices made in small quantities. A substantial amount of hand assembly by skilled workers is required to produce the devices. It would be desirable to develop a rate of angular acceleration sensor which can be simply and inexpensively manufactured.